In my Thomas bus, that handle is a release for the doors. It is attached to a cable that is attached to a locking plate inside the bus. If I don't throw that lever, I cannot open the doors. My guess is that someone disconnected your lever and the locking device inside the bus so the doors can be pulled open directly. My lever has a small cabinet lock in it which will prevent the lever from moving, and I had a key made, but the key does not operate smoothly at all, so I will need to come up with a different locking mechanism, or I suppose I could try to fix the lever/lock.